JP2023111950A - Speed reducer - Google Patents

Abstract

To provide a speed reducer with good workability when machining a workpiece which is to be a machining material for a member with a hole.SOLUTION: A speed reducer comprises a rolling contact surface on which a rolling element rolls and a member with a hole on which the hole is disposed. In the speed reducer, a base material area 42 and a surface hardened layer 44 with hardness higher than the base material area 42 on a surface side from the base material area 42 are disposed in the member with the hole; on the surface hardened layer 44, a surface layer area 46 and a hardness transition area 48 are disposed in this order toward a depth direction perpendicular from the surface; when the amount of change in Vickers hardness per 0.1 mm with respect to the depth direction is set to a hardness change amount, the surface layer area 46 continues to the hardness transition area 48 from the surface, and includes portions where the hardness change amount is 0 or more; the hardness transition area 48 is continuously reduced in hardness toward the depth direction, and includes portions where the hardness change amount is -60 or less; the rolling contact surface is disposed on the surface of the surface layer area 46; and the hole is disposed in the base material area 42.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD The present invention relates to a speed reducer and a work machining method.

Patent Literature 1 describes a flexural mesh type speed reducer. In this reduction gear transmission, rolling elements are arranged between the casing and the output-side flange body, and the output-side flange body is rotatably supported by the casing via the rolling elements. The output-side flange body has a rolling surface on which the rolling element rolls and a hole into which a bolt is screwed.

JP 2011-112214 A

A component having a rolling contact surface, such as the output side flange body of Patent Document 1, is required to increase the hardness of the rolling contact surface in order to improve fatigue strength. In order to achieve this, generally, a surface hardening treatment capable of hardening the entire workpiece to be heat treated, such as through hardening, is used.

In the case of a member with a hole such as the output-side flange body described above, there is a case where the work is subjected to the surface hardening treatment before the hole is formed in the work. In this case, if the entire workpiece is hardened by quenching, problems such as shortening of tool life will occur during drilling. There has not yet been proposed a deceleration device that is devised in relation to the workability of the work that is the material for such a holed member.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a speed reduction gear which has good machinability for a work that is a material for forming a member with a hole.

One aspect of the present invention relates to a reduction gear transmission. The speed reducer is a speed reducer including a member with a hole provided with a rolling surface on which the rolling element rolls and a hole, wherein the member with the hole includes a base material region and a surface side of the base material region. A hardened surface layer having a hardness higher than that of the base material region is provided in the hardened surface layer, and a surface layer region and a hardness transition region are provided in order in the depth direction perpendicular to the surface from the surface, and the depth direction When the amount of change in Vickers hardness per 0.1 mm is the amount of change in hardness, the surface layer region is continuous from the surface to the hardness transition region, includes a portion where the amount of change in hardness is 0 or more, and the hardness The transition region includes a portion where the hardness continuously decreases in the depth direction and the hardness change amount is −60 or less, the rolling surface is provided on the surface of the surface region, and the hole A portion is provided in the base material region.

Another aspect of the present invention relates to a method of processing a workpiece. The present method is a method for processing a work that is a material for a member with a hole, wherein the member with a hole is provided with a rolling surface on which the rolling element rolls and a hole, and the rolling surface of the work is A quenching step of irradiating a laser beam to a portion to be a surface to provide a hardened surface layer, leaving a base material region without quenching a portion to be a hole of the work, and a quenching step of leaving the base material region. and a drilling step of drilling the base material region at the site to be.

Advantageous Effects of Invention According to the present invention, it is possible to provide a reduction gear device having good machinability when working a work that is a material for a member with a hole.

It is a sectional view showing a reduction gear transmission of a 1st embodiment. 2 is an enlarged view showing the rolling element of FIG. 1 together with its peripheral structure; FIG. It is a figure which shows typically the hardness distribution of the 1st carrier member of 1st Embodiment. 4 is a graph showing an example of hardness distribution of the first carrier member of the first embodiment; 8 is another graph showing an example of the hardness distribution of the first carrier member of the first embodiment;

Hereinafter, in the embodiments and modified examples, the same constituent elements are denoted by the same reference numerals, and overlapping descriptions are omitted. Moreover, in each drawing, for convenience of explanation, some of the constituent elements are appropriately omitted, and the dimensions of the constituent elements are shown by appropriately enlarging or reducing them. In addition, separate components that have something in common are distinguished by adding "first, second" etc. at the beginning of the name and adding "-A, -B" etc. at the end of the code to distinguish and collectively Sometimes these are omitted.

FIG. 1 is a cross-sectional view showing the speed reduction gear 10 of the first embodiment. The speed reducer 10 of the present embodiment is a flexural mesh type speed reducer that rotates the external gear 22 meshing with the internal gear 24 while flexing and deforming the external gear 22 and outputs the rotation component.

The reduction gear 10 mainly includes a casing 12, a pair of carriers 14, a plurality of rolling elements 16, a vibrating body 18, a vibrating body bearing 20, an external gear 22, an internal gear 24, Prepare.

The casing 12 is a cylindrical member, inside which a pair of carriers 14 are arranged. A pair of carriers 14 are tubular members having rigidity. A pair of carriers 14 are arranged with an interval in the axial direction X, which will be described later, and a vibrating body 18 is arranged inside them.

One carrier 14 (the carrier on the right side in the drawing; hereinafter referred to as an input side carrier 14-A) is non-rotatably assembled to the casing 12 with bolts 26. As shown in FIG. The input-side carrier 14-A is connected to a driving device such as a motor by means of bolts (not shown) screwed into bolt holes 28. As shown in FIG.

The other carrier 14 (the carrier on the left side in the drawing; hereinafter referred to as an output side carrier 14-B) is rotatably supported by the casing 12 via rolling elements 16. As shown in FIG. The output side carrier 14-B functions as an output section for outputting the rotation input from the driving device to the driven device to be driven. Hereinafter, the direction along the rotation center line La of the output carrier 14-B will be described as the axial direction X. As shown in FIG. Details of the casing 12, the output side carrier 14-B, and the rolling elements 16 will be described later.

The vibrating body 18 is a tubular member having an elliptical cross-sectional shape. The vibrating body 18 is rotatably supported by the pair of carriers 14 via bearings 30 . A drive shaft of a drive device is connected to the vibrating body 18 .

The vibration generator bearing 20 is arranged between the vibration generator 18 and the external gear 22 . The vibration generator bearing 20 rotatably supports the external gear 22 with respect to the vibration generator 18 .

The external gear 22 is arranged on the outer peripheral side of the vibrating body 18 . The external gear 22 is a flexible annular member. The external gear 22 is flexurally deformed into an elliptical shape by the vibrating body 18 via the vibrating body bearing 20 . The external gear 22 has an annular base portion 22a, and a first external tooth portion 22b and a second external tooth portion 22c integrally formed on the outer peripheral side of the base portion 22a. The first external toothed portion 22b and the second external toothed portion 22c are arranged in the axial direction X. As shown in FIG. When the vibrating body 18 rotates, the external gear 22 is flexurally deformed so as to match the shape of the vibrating body 18 while changing the meshing position with the internal gear 24 in the circumferential direction.

The internal gear 24 is a rigid annular member. The internal gear 24 is arranged on the outer peripheral side of the external gear 22 . The internal gear 24 includes a first internal gear 24-A with which the first external tooth portion 22b of the external gear 22 internally meshes, and a second internal gear 24-A with which the second external tooth portion 22c of the external gear 22 internally meshes. 2 internal gears 24-B. The external toothed portions 22b and 22c are internally meshed with the internal gear 24 on both sides of the vibrating body 18 in the longitudinal direction. The number of internal teeth of the first internal gear 24-A is greater than the number of external teeth of the first external tooth portion 22b by 2i (i is a natural number equal to or greater than 1), and the second internal gear 24-B is the second external gear. The number of internal teeth is the same as the number of external teeth of the tooth portion 22c. The first internal gear 24-A is integrally formed with the input side carrier 14-A, and the second internal gear 24-B is integrally formed with the output side carrier 14-B.

The operation of the above reduction gear 10 will be described.
When the drive shaft rotates, the vibrating body 18 rotates together with the drive shaft. When the vibrating body 18 rotates, the external gear 22 is continuously flexurally deformed so as to match the shape of the vibrating body 18 while changing the meshing position with the internal gear 24 in the circumferential direction. The first external toothed portion 22b rotates relative to the first internal gear 24-A by the amount corresponding to the difference in the number of teeth from the first internal gear 24-A each time the vibrating body 18 rotates once. (rotate). At this time, the rotation of the vibrating body 18 is reduced at a reduction ratio corresponding to the difference in the number of teeth from the first internal gear 24-A, and the external gear 22 rotates.

The first external toothed portion 22b rotates integrally with the second external toothed portion 22c in the same phase. Since the second internal gear 24-B has the same number of teeth as the second external toothed portion 22c, the relative meshing position with the second external toothed portion 22c changes before and after the vibrating body 18 rotates once. synchronously with the same rotation component as the first external toothed portion 22b. The rotation component of the first external toothed portion 22b is transmitted to the output side carrier 14-B via the second internal gear 24-B. As a result, the rotation of the vibrating body 18 is decelerated and output from the output side carrier 14-B to the driven device.

A configuration around the rolling element 16 will be described.
FIG. 2 is an enlarged view showing the rolling element 16 of FIG. 1 together with its peripheral structure. A plurality of rolling elements 16 cooperate with the output side carrier 14-B and part of the casing 12 to form a bearing. The rolling elements 16 of this embodiment cooperate with the output side carrier 14-B and part of the casing 12 to form a cross roller bearing. A plurality of rolling elements 16 are provided at intervals in the circumferential direction around the rotation center line La of the output carrier 14-B. The rolling elements 16 of this embodiment are cylindrical rollers that serve as cross rollers of a cross roller bearing. The plurality of rolling elements 16 are alternately arranged in the circumferential direction so that their rolling shafts extend toward one side in the axial direction X toward the rotation center line La and those extending in the other side in the axial direction X. .

The output side carrier 14-B and the casing 12 are arranged with a plurality of rolling elements 16 interposed therebetween. The output side carrier 14-B is arranged on the inner peripheral side, and the casing 12 is arranged on the outer peripheral side. The output side carrier 14-B has a tubular first carrier member 32 and a tubular second carrier member 34 connected to the first carrier member 32 by spigot fitting or the like.

V-shaped grooves 36 are formed in the first carrier member 32 and the casing 12 at locations facing each other in the radial direction. Each of the pair of inner side surfaces of the V-shaped groove 36 of the first carrier member 32 serves as a first rolling surface 38-A on which the rolling element 16 rolls. Each of the pair of inner side surfaces of the V-shaped groove 36 of the casing 12 serves as a second rolling surface 38-B on which the plurality of rolling elements 16 roll. The first rolling surface 38-A and the second rolling surface 38-B are provided at locations facing each other in the radial direction with the plurality of rolling elements 16 interposed therebetween.

The first carrier member 32 is a member with a first hole provided with a first hole portion 40-A in addition to the above-described first rolling surface 38-A. The first rolling surface 38 -A is formed on the outer peripheral surface of the cylindrical portion of the first carrier member 32 . The first hole portion 40-A is provided at a position shifted to one side in the axial direction X from the first rolling surface 38-A. A female screw portion is formed in the first hole portion 40-A of the present embodiment, and a bolt (not shown) for connecting with a driven device is screwed therein.

The casing 12 is a member with a second hole provided with a second hole 40-B in addition to the second rolling surface 38-B described above. A second rolling surface 38 -B is formed on the inner peripheral surface of the cylindrical portion of the casing 12 . The second hole portion 40-B is provided at a position shifted to the other side in the axial direction X from the second rolling surface 38-B. A female screw is formed in the second hole portion 40-B of the present embodiment, and a bolt 26 for assembling the input side carrier 14-A is screwed therein.

The first carrier member 32 and the casing 12 are arranged so that the rolling elements 16 roll on the first rolling surface 38-A of the first carrier member 32 and roll on the second rolling surface 38-B of the casing 12. Relative rotation accompanies the rolling of the moving body 16 . At this time, the first carrier member 32 also functions as an inner ring for the rolling elements 16 , and the casing 12 also functions as an outer ring for the rolling elements 16 . The first carrier member 32 and the casing 12 function as a first member and a second member that are relatively rotatable as the rolling elements 16 roll.

The first carrier member 32 is provided with a first rolling surface 38-A and a first bore 40-A as part of a single member. The casing 12 is provided with the second rolling surface 38-B and the second hole 40-B as part of a single member. This means that the rolling surface 38 and the bore 40 are not provided separately on separate members, but are provided as part of a single piece (single member).

Here, in the present embodiment, the hardness distribution of each of the first carrier member 32 and the casing 12 is characteristic. This hardness distribution is common to each of the first carrier member 32 and the casing 12 . Hereinafter, the hardness distribution of the first carrier member 32 will be mainly described, and the description of the hardness distribution of the casing 12 will be omitted.

FIG. 3 is a diagram schematically showing the hardness distribution of the first carrier member 32. As shown in FIG. The first carrier member 32 is made of, for example, a machine structural alloy steel material such as chromium molybdenum steel material (SCM material in JIS), that is, metal. The first carrier member 32 is subjected to surface hardening treatment by laser hardening, and a surface hardened layer 44 is provided in addition to the base material region 42 .

The base material region 42 is an unhardened region that has not been hardened. The base material region 42 is a region having the hardness of the base material itself of the work that is the processing material of the first carrier member 32 .

The hardened surface layer 44 is provided closer to the surface than the base material region 42 . The hardened surface layer 44 is a region hardened by performing surface hardening treatment by quenching, and has higher hardness than the base material region 42 . The hardened surface layer 44 is provided with a quenched structure containing, for example, martensite as a main phase. The hardened surface layer 44 is provided only on a portion of the entire surface of the first carrier member 32 including the rolling surface 38 , and is not provided on the peripheral portion including the hole 40 .

FIG. 4 is a graph showing an example of hardness distribution of the first carrier member 32. As shown in FIG. This graph shows the relationship between the depth from the surface of the hardened surface layer 44 and the Vickers hardness. This graph shows the hardness distribution of the first carrier members 32 of Examples 1 and 2, which will be described later. In this graph, when the direction perpendicular to the surface (rolling surface 38) of the hardened surface layer 44 is defined as the depth direction Pa, Vickers hardness measured at a plurality of points in the depth direction Pa from the surface of the hardened surface layer 44 is plotted. Vickers hardness is measured by a method according to JIS Z2244.

The numbers attached to the measurement points in the graph indicate the amount of change in Vickers hardness (hereinafter referred to as hardness change amount) from the adjacent measurement point on the surface side. The amount of change in hardness indicates the amount of change in Vickers hardness per 0.1 mm with respect to the depth direction Pa of the hardened surface layer 44 and the base material region 42 .

The hardened surface layer 44 is provided with a surface region 46 and a hardness transition region 48 in order from the surface of the hardened surface layer 44 in the depth direction Pa (see also FIG. 3). The surface layer region 46 is continuous from the surface of the hardened surface layer 44 to the hardness transition region 48 . Hardness transition region 48 is continuous from surface layer region 46 to base material region 42 . In the hardness transition region 48, the hardness continuously decreases in the depth direction Pa (that is, the hardness change amount never becomes 0 or more), and the hardness of the base material region 42 changes from the hardness of the surface layer region 46. becomes a transition region.

The hardness transition region 48 includes a location where the hardened surface layer 44 has a sharp decrease in hardness in the depth direction Pa from the surface of the hardened surface layer 44, and includes a location where the amount of change in hardness is at least −60 or less, and usually −100 or less. The hardness transition region 48 is a region including a portion where the hardness change amount is at least −60 or less, usually −100 or less, and the hardness change amount changes from a value of 0 or more to a negative value in the depth direction Pa. This is the area starting from the switching point. The hardness transition region 48 has a hardness change amount of -200 or more and less than 0, for example. The length of the hardness transition region 48 in the depth direction Pa ranges, for example, from 0.3 mm to 0.8 mm. The presence of the hardness transition region 48 where the hardness sharply decreases makes it easy to reduce the total hardened layer depth, which is the depth from the surface of the surface hardened layer 44 to the base material region 42 .

The surface layer region 46 is a region existing between the surface of the hardened surface layer 44 and the hardness transition region 48 . In order to specify this, the surface layer region 46 is conditioned to include a portion where the amount of change in hardness is 0 or more. In addition, even when the hardness change amount becomes a negative value, the surface layer region 46 has a larger hardness change amount (absolutely ), the hardness does not decrease as sharply as in the hardness transition region 48 . The surface layer region 46 can also be regarded as a region in which the amount of change in hardness exceeds at least -60. Due to the presence of such a surface layer region 46, a region having a hardness higher than that of the base material region 42 is present between the surface of the surface hardened layer 44 and the hardness transition region 48, and the depth of the effective hardened layer having the required hardness is increased. It becomes easier to ensure the

The surface layer region 46 is also a region that contributes to ensuring the depth of the effective hardened layer having the required hardness without a large increase or decrease in Vickers hardness. In order to achieve this, the surface layer region 46 has a first difference value Δ, which is the difference between the maximum value and the minimum value of Vickers hardness, of 100 or less, and the hardness variation is in the range of more than −60 and less than or equal to +60. The maximum value and minimum value of Vickers hardness herein refer to the maximum value and minimum value when the Vickers hardness of the surface layer region 46 is measured in units of 0.1 mm in the depth direction Pa.

The surface layer region 46 has, for example, a Vickers hardness of at least 1.5 times the Vickers hardness at the starting position of the base material region 42 in order to ensure the depth of the effective hardened layer having the required hardness. In addition, the surface layer region 46 is provided in a range of at least 0.2 mm from the surface of the surface hardened layer 44 in order to secure the depth of the effective hardened layer. Although the lower limit of the Vickers hardness of the surface layer region 46 is not particularly limited, it is preferably 600 or more, for example, from the viewpoint of ensuring sufficient fatigue strength. Although the upper limit of the Vickers hardness of the surface layer region 46 is not particularly limited, it is, for example, 800 or less.

The base material region 42 starts from a location where the hardness change amount switches from a negative value to a value of 0 or more in the depth direction Pa from the hardness transition region 48 . In the base material region 42, the hardness does not greatly increase or decrease in the depth direction Pa. Based on this relationship, the base material region 42 has, for example, a second difference value Δ, which is the difference between the maximum value and the minimum value of Vickers hardness, of 50 or less, and a hardness change amount of -50 or more and +50 or less. Therefore, even if it is considered that the base material region 42 starts from the point where the hardness change amount is -50 or more and +50 or less in the depth direction Pa from the point where the hardness change amount of the hardness transition area 48 is -60 or less. good. The specific hardness of the base material region 42 is not particularly limited, but ranges from 250 to 400 Hv, for example.

The above hardness conditions may be satisfied in a range extending from the central portion 38a (see FIG. 3) in the width direction Pb of the rolling surface 38 toward the depth direction Pa. The width direction Pb here refers to a direction orthogonal to the depth direction Pa of the rolling surface 38 in a cross section obtained by cutting the first carrier member 32 along the rotation center line La (see FIG. 1).

In the first carrier member 32 described above, the rolling surface 38 is provided on the surface of the surface layer region 46 and the first hole portion 40 -A is provided on the base material region 42 . That is, the first hole portion 40-A is provided only in the base material region 42 and not provided in the hardened surface layer 44. As shown in FIG. Therefore, for the work that is the material to be processed for the first carrier member 32, the perforating process for forming the first holes 40-A in the low-hardness base material region 42 instead of the high-hardness hardened surface layer 44 can be performed. Therefore, the workability of the workpiece is improved.

Further, since the surface hardened layer 44 is provided with the surface layer region 46 in which the hardness does not decrease sharply in the depth direction Pa, it becomes easy to secure the depth of the effective hardened layer. Further, since the surface hardened layer 44 is provided with the hardness transition region 48 in which the hardness sharply decreases in the depth direction Pa, the total hardened layer depth can be easily reduced. Therefore, by bringing the hole portion 40 closer to the rolling surface 38, a design for miniaturizing the first carrier member 32 is allowed. In the example of the present embodiment, by bringing the hole 40 closer to the rolling contact surface 38 in the axial direction, a design that reduces the size of the first carrier member 32 in the axial direction is allowed. As a result, it becomes easy to achieve not only the above-described good workability when working the workpiece, but also a sufficient effective hardened layer depth of the hardened surface layer 44 and a reduction in the size of the first carrier member 32 in a well-balanced manner.

Further, the first carrier member 32 is provided with the first rolling surface 38-A and the first hole 40-A as part of a single member. Therefore, the aforementioned effects can be obtained without increasing the number of parts of the reduction gear transmission 10 .

Next, preferable conditions for hardness distribution of the first carrier member 32 will be described.
The depth from the rolling surface 38 on the surface of the surface layer region 46 to the starting point of the hardness transition region 48 (hereinafter referred to as transition start depth) is preferably in the range of 0.5 mm to 1.5 mm. If the transition starting depth is less than 0.5 mm, the starting point of the hardness transition region 48 becomes too shallow, and the depth of the effective hardened layer may be insufficient. If the transition starting depth exceeds 1.5 mm, the starting point of the hardness transition region 48 becomes too deep, and the distance from the rolling contact surface 38 to the hole portion 40 is too large to ensure workability during processing of the workpiece. It may take longer. If the condition of the transition start depth is satisfied, the above-mentioned workability at the time of processing the workpiece, sufficient effective hardened layer depth of the surface hardened layer 44, and miniaturization of the first carrier member 32 can be well balanced. easier to implement.

The distance from the rolling surface 38 on the surface of the surface layer region 46 to the starting point of the base material region 42, that is, the depth from the rolling surface 38 to the end point of the hardness transition region 48 (hereinafter referred to as transition end depth) is preferably in the range of 0.8 mm to 2.0 mm. If the transition end depth is less than 0.8 mm, the end point of the hardness transition region 48 becomes too shallow, and the depth of the effective hardened layer may be insufficient. If the transition end depth exceeds 2.0 mm, the end point of the hardness transition region 48 becomes too deep, and the distance from the rolling surface 38 to the hole portion 40 is is likely to be long. If this transition end depth condition is satisfied, the above-described workability during processing of the workpiece, sufficient effective hardened layer depth of the surface hardened layer 44, and miniaturization of the first carrier member 32 can be well balanced. easier to implement.

FIG. 5 is another graph showing an example of the hardness distribution of the first carrier member 32. As shown in FIG. This graph shows the hardness distribution of the first carrier members 32 of Examples 3 and 4 and Reference Examples 1 and 2, which will be described later. Although the details will be described later, in Examples 1 to 4, laser hardening is used as the surface hardening treatment for the rolling surface 38 of the first carrier member 32 . On the other hand, Reference Example 1 uses nitriding treatment, and Reference Example 2 uses induction hardening.

The conditions for the transition start depth and the transition end depth described above can be satisfied by using laser hardening as the surface hardening treatment. When nitriding treatment is used as the surface hardening treatment, as shown in Reference Example 1, hardening is performed only in a very shallow range from the rolling surface 38 of the first carrier member 32 in the depth direction Pa. In this case, the surface layer region 46 does not exist in the hardened surface layer 44 . In this case, the transition start depth is in the range of 0.1 mm to 0.2 mm, and the transition end depth is in the range of less than 0.8 mm, neither of the conditions being satisfied. When induction hardening is used as the surface hardening treatment, as shown in Reference Example 2, hardening is performed over a very deep range from the rolling surface 38 of the first carrier member 32 in the depth direction Pa. In this case, the transition start depth and the transition end depth exceed 2.0 mm, and neither condition can be satisfied. Although not shown, when induction hardening is used as the surface hardening treatment, the transition start depth and transition end depth are 5.0 mm or more. The distance from the rolling contact surface 38 to the hole 40 becomes too long in order to ensure workability during machining of the workpiece.

The hardened surface layer 44 described above is provided over the entire circumference of the rolling surface 38 of the first carrier member 32 . Such a hardened surface layer 44 is obtained by water-cooling the workpiece at the same time as the laser hardening, as will be described later.

Next, a method for processing a workpiece that is a material for the first carrier member 32 will be described.
This processing method includes a quenching process of quenching the work and a drilling process of drilling the work. A workpiece to be processed by this processing method is prepared by cutting or the like. The workpiece to be machined has a shape in which the holes 40 are not formed in the portions of the first carrier member 32 that are to become the holes 40 .

In the quenching process, laser quenching is used in which the workpiece is quenched using a laser beam. In the hardening process, the workpiece is rotatably supported around the rotation center line La by a rotating jig (not shown). A laser beam of a predetermined output is irradiated from a laser head to a portion of the workpiece which is to become the rolling surface 38 . The laser light output is set so as to obtain a temperature rise state exceeding the quenching temperature according to the composition of the workpiece. A laser beam is emitted from the laser head to a range covering the entire length in the width direction Pb of the portion to be the rolling surface 38 of the workpiece. In this state, the work is rotated around the rotation center line La at a predetermined rotational speed, thereby hardening the portion of the work that is to become the rolling surface 38 in the circumferential direction. As a result, a hardened surface layer 44 is provided from the surface toward the depth direction Pa at the portion of the workpiece that is to become the rolling surface 38 . At this time, the laser beam is not irradiated to the portion of the workpiece that is to become the hole portion 40 so as not to be quenched, leaving the base material region 42 .

The hardness distribution of the hardened surface layer 44 corresponds to the composition of the workpiece. Therefore, a workpiece having a composition that satisfies the hardness distribution of the conditions described above is prepared. The composition of this work is, for example, a chromium molybdenum steel material such as SCM440 or AISI4150, but is not limited to these and may be determined by experimental examination.

In the quenching step of the present embodiment, quenching is performed so that a hardened surface layer 44 is provided over the entire circumference of the portion of the work that is to become the rolling contact surface 38 . In order to achieve this, a workpiece rotating at a predetermined rotational speed is irradiated with a laser beam of a predetermined output to be quenched and water-cooled. The rotation speed and output are set to a sufficiently high rotation speed and a sufficiently high output so as to obtain a simulated temperature rise state in which the ring-shaped coil heats. Water cooling is performed in order to secure the cooling rate necessary for hardening, since self-cooling, which is a feature of laser hardening, becomes difficult due to the use of a high-output laser beam. The rotational speed, the magnitude of the laser light output, and the water cooling conditions may be determined by, for example, experimental studies.

In the piercing step, the base material region 42 located at the portion to be the hole portion of the work quenched in the quenching step is pierced. In the piercing step of the present embodiment, a tap is used to pierce a portion of the work that is to become the hole, thereby forming an internal thread portion. At this time, since the base material region 42 is provided in the portion of the work that is to become the hole portion, workability during processing of the work is improved.

In the quenching process, an absorbent having a high heat absorption rate may be applied to the surface of the portion of the work that is to become the rolling surface 38, and then the absorbent may be irradiated with laser light. This absorbent material is, for example, graphite or the like. As a result, it is possible to increase the amount of heat absorption in the portion of the work that is to become the rolling surface 38, and to deepen the transition start depth and the transition end depth of the holed member obtained through the piercing process of the work. can.

Examples of the present invention will be described below. The examples are only examples for suitably explaining the present invention, and are not intended to limit the present invention in any way.

First, a work having the outer shape of the first carrier member 32 described above was produced as a trial. Examples 1, 3, and 4 and Reference Examples 1 and 2 include works using SCM440, and Example 2 using AISI4150.

A plurality of types of surface hardening treatments were applied to the rolling contact surface 38 of the prototype work. In Examples 1 and 3, the work was quenched by being heated at a temperature equal to or higher than the quenching temperature by laser quenching while the work was rotated, and cooled by water cooling. In Examples 2 and 4, surface hardening treatment by laser hardening was performed under the same conditions as in Examples 1 and 3, except that the rolling surface 38 of the workpiece was coated with graphite as an absorbing material. In Reference Example 1, the rolling surface 38 of the work was surface-hardened by nitriding using a fluorine-based gas. In Reference Example 2, the rolling contact surface 38 of the workpiece was surface-hardened by induction hardening. This induction hardening was performed by heating at a temperature equal to or higher than the hardening temperature and then cooling with water.

From the surface-hardened workpiece, test pieces were cut out from a plurality of locations in the depth direction Pa from the rolling surface 38, and the plurality of test pieces were subjected to a Vickers hardness test.

4 shows test results of Examples 1 and 2. FIG. FIG. 5 shows the test results of Examples 3 and 4 and Reference Examples 1 and 2. As shown in FIGS. 4 and 5, in Examples 1 to 4 in which laser hardening is performed, the hardened surface layer 44 is provided with a surface layer region 46 and a hardness transition region 48 that satisfy the hardness distribution described above. The first difference value Δ between the maximum value and the minimum value of the Vickers hardness of the surface layer region 46 is 44.4, 97.3, 35.8 and 50.1 in Examples 1 to 4, respectively.

Exemplary embodiments of the present invention have been described above in detail. All of the above-described embodiments merely show specific examples for carrying out the present invention. The contents of the embodiments do not limit the technical scope of the present invention, and many design changes such as changes, additions, and deletions of constituent elements can be made without departing from the spirit of the invention defined in the claims. It is possible. In the above-described embodiment, descriptions such as "of the embodiment", "in the embodiment", etc. are added to the contents that allow such design changes. Changes are not unacceptable. Moreover, the hatching attached to the cross section of the drawing does not limit the material of the hatched object.

Although the speed reducer 10 has been described as an example of a flexural mesh type speed reducer, its type is not particularly limited. For example, it may be an eccentric oscillating type speed reducer, or a speed reducer including any of a planetary gear mechanism, an orthogonal shaft gear mechanism, a parallel shaft gear mechanism, and the like. Further, although the cylindrical flexural mesh type reduction gear transmission has been described as an example, the type of the flexural mesh type reduction gear transmission is not particularly limited. For example, the internal gear may be applied to one cup-type or top hat-type flexure mesh type reduction gear.

Although the casing 12 and the first carrier member 32 have been described as examples of the perforated member provided with the rolling surface 38 and the hole portion 40, the specific example is not limited to this. Moreover, although the example in which both the first member and the second member arranged with the rolling element 16 interposed therebetween is a member with a hole has been described, at least one of them may be a member with a hole.

When laser quenching is used as the surface hardening treatment, the above conditions regarding the hardness distribution of the holed member can be satisfied by appropriately setting the composition of the workpiece and the heat treatment conditions. Here, the conditions regarding the hardness distribution refer to numerical conditions regarding the point that the surface layer region 46 and the hardness transition region 48 are provided in the hardened surface layer 44 and the transition start depth and transition end depth. The heat treatment conditions here refer to, for example, the power (kW) of the laser beam irradiated to the work and the conditions regarding the presence or absence of coating of an absorbent on the surface of the work. When the output of this laser beam is increased, the range of quenching from the rolling surface of the holed member in the depth direction Pa expands, making it easier to deepen the transition start depth and the transition end depth. Further, when the absorbent is applied to the surface of the workpiece, the transition start depth and the transition end depth can be easily increased compared to when the absorbent is not applied. Various conditions for satisfying the aforementioned hardness distribution of the holed member may be determined through experiments, analyses, etc., taking into account such matters.

In the embodiments, laser hardening was described as an example of surface hardening applied to the member with holes, but the present invention is not limited to this. This surface hardening treatment continues from the surface of the holed member to the hardness transition region, and the surface layer region including the portion where the hardness change amount is 0 or more, and the hardness continuously decreases in the depth direction. Anything that can obtain a hardness transition region including a point where the amount becomes -60 or less is acceptable.

DESCRIPTION OF SYMBOLS 10... Reduction gear, 16... Rolling element, 38... Rolling surface, 40... Hole, 42... Base material area, 44... Hardened surface layer, 46... Surface layer area, 48... Hardness transition area.

Claims (4)

A reduction gear including a member with a hole provided with a hole,
The member with holes is provided with a base material region and a hardened surface layer having a hardness higher than that of the base material region on the surface side of the base material region,
The hardened surface layer is provided with a surface layer region and a hardness transition region in order in the depth direction perpendicular to the surface,
When the amount of change in Vickers hardness per 0.1 mm in the depth direction is defined as the amount of change in hardness,
The surface layer region is continuous from the surface to the hardness transition region and includes a portion where the hardness change amount is 0 or more,
The hardness transition region includes a location where the hardness continuously decreases in the depth direction and the hardness change amount is -60 or less,
The depth from the surface of the surface region to the hardness transition region is less than 1.5 mm,
The reduction gear is provided in the base material region, wherein the hole overlaps the surface in the depth direction or overlaps the hardened surface layer in the drilling direction of the hole. 2. The reduction gear transmission according to claim 1, wherein the depth from the surface of said surface layer region to said hardness transition region is in the range of 0.5 mm to 1.5 mm. 3. The reduction gear transmission according to claim 1, wherein the depth from the surface of said surface layer region to said base material region is in the range of 0.8 mm to 2.0 mm. 3. The reduction gear transmission according to claim 1, wherein the holed member has the portion provided with the hardened surface layer and the hole portion as a part of a single member.

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